Torque converter having both a lock-up clutch and a disengaging clutch mechanism

ABSTRACT

A torque converter is provided with both a lock-up clutch and a disengaging clutch for use with a manual transmission. When the disengaging clutch is engaged, torque is transmittable through a torque converter impeller and turbine fluid coupling. When the lock-up clutch is engaged, torque is mechanically transmitted through the lock-up clutch to a manual transmission input shaft. A single control mechanism effects selective engagement and disengagement of both the lock-up clutch and the disengaging clutch. In an alternate embodiment of the present invention, a weight may be engaged and disengaged from various components within the torque converter to change the ratio of a moment of inertia of a power input mechanism and a power output mechanism defined by portions of the torque converter. A lock-up clutch in the alternate embodiment and the weight are also engaged and disengaged by a single control mechanism.

The following application is a division of U.S. Ser. No. 08/912,579,filed Aug. 18, 1997, now U.S. Pat. No. 5,881,852, which is a division ofU.S. Ser. No. 08/603,043, filed Feb. 16, 1996, now U.S. Pat. No.5,695,028. The entire disclosure of U.S. Ser. No. 08/912,579, filed Aug.18, 1997 is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to a torque converter used fortransmitting torque from a crank shaft of an engine to a manualtransmission, and in particular, the present invention relates to atorque converter having both a lock-up clutch and a disengaging clutchmechanism.

B. Description of the Related Art

Recently, automotive manufacturers have begun using a torque converterswith manual transmissions. Torque converters, in general, include aconverter housing with an impeller formed on an inner surface of thehousing, a turbine rotatably supported within the housing and a statorrotatably supported within the housing between the turbine and theimpeller. The converter housing is typically formed with power inputfront cover which is connected to the crankshaft of an engine. One suchtorque converter is disclosed in Japanese Unexamined Utility Model No.SHO/64/31355, for example. In such a torque converter, a disengagingclutch couples the turbine and a power input shaft of a transmissionallowing the torque converter to be manually engaged and disengaged toaccommodate use with a manual transmission. The disengaging clutch isconnected to one surface of the turbine. In other torque converters, alock-up clutch may also be provided to directly couple the power inputfront cover with the turbine.

When starting a vehicle equipped with a torque converter and a manualtransmission, torque is applied from the power input front cover to animpeller of the torque converter, causing the impeller to urge fluidwithin the torque converter to move toward the impeller causing theturbine to rotate. As a result, the vehicle starts to move smoothly.When the speed of rotation of a power input shaft of the transmissionreaches a predetermined level, the lock-up clutch engages so that thetorque is transmitted directly from the power input front cover to thepower input shaft of the transmission. Since the torque is mechanicallytransmitted, the vehicle runs with greater fuel efficiency. Whenchanging gears, the disengaging clutch is operated and the gears of themanual transmission may be shifted.

One drawback to the above-described configuration is that the torqueconverter has a rather complicated configuration in that the disengagingclutch and the lock-up clutch require separate mechanisms for engagementand disengagement. Such a configuration is complicated and expensive tomanufacture.

There are torque converter configurations where the lock-up clutchincludes a piston capable of being urged into press-contact with theinner surface of the front cover of the torque converter housing forengagement of the lock-up clutch. The lock-up clutch may further includea plurality of coil springs coupling the piston with the power outputelement. Another prior art torque converter includes a frictionresistance generating mechanism which generates friction resistance whentorsional vibration is applied to a lock-up clutch.

In such lock-up clutches, torsional rigidity of the coil spring must bereduced in order to effectively dampen torsional vibration under smallload conditions. It is possible to reduce the wire diameter of thespring coil in order to reduce the torsional rigidity of the coilspring, however reducing the wire diameter also causes a correspondingreduction in the overall torque transmission capability of the torqueconverter. Thus, the coil diameter of the coil spring is usually kept ata relatively large diameter so that capacity of torque transmission isretained. However, the torsional rigidity of the torque converter isincreased as a result. Further, the large diameter coil spring occupiesa larger space, thus preventing downsizing the lock-up clutch.

In order to reduce the transmission from developing abnormal sounds likeclattering sound and internal indistinct sounds during ordinary drivingconditions, it is desirable for the resonance frequency of the torqueconverter to be reduced to a level generally equal to or below the idlespeed of the engine associated with the torque converter and manualtransmission.

In the above-described prior art torque converter and the vehicle inwhich it is used, under the ordinary driving conditions where thelock-up clutch operates, the power transmission system may be dividedinto a power input portion and a power output portion which areseparated by the coil spring of the lock-up clutch therebetween. Thedynamic characteristics of the power input portion and the power outputportion must be evaluated in order to design a torque converter whichprovides adequate vibration reduction and reliable torque transmission.Ideally, in a power transmission system, it is necessary to sufficientlyincrease a ratio of moment of inertia of the power output portion to thepower input portion to reduce the resonance frequency to be equal to orless than the idle speed of the engine. However, when the lock-up clutchis disengaged, it is desirable to reduce an inertial mass of a poweroutput portion so as not to exert an adverse effect to components likeclutches.

A centrifugal mechanism has been used to couple and uncouple an annularweight to the lock-up clutch. In such a design, as the speed of rotationof the turbine increases, centrifugal force works so that the annularweight is coupled to power output elements including the turbine.Consequently, the ratio of moment of inertia of the power output portionto that of the power input portion becomes larger, and the resonancefrequency can be reduced to a low frequency region in a drive system. Asthe speed of rotation of the turbine is reduced, the annular weight isuncoupled from the power output elements like the turbine. This iseffective to avoid some causes of malfunctions of components in clutchesand transmission.

A disadvantage to the annular weigh configuration is that the couplingand uncoupling of the weight in the prior art is effected using acentrifugal mechanism, and therefore accurate control of coupling anduncoupling is dependent upon centrifugal forces. Such forces may notprovide adequate or desirable control for coupling and uncoupling of theannular weight.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention to simplify an innerconfiguration of a torque converter which has a disengaging clutch and alock-up clutch.

It is another object of the present invention to downsize the width ofspring elements while maintaining desired spring characteristics.

It is another object of the present invention to downsize axialdimensions of a lock-up clutch mechanism.

Another object of the present invention is to control coupling anduncoupling of a weight element to portions within a torque converterhousing.

In a first aspect of the present invention, a torque converter fortransmitting torque from a crank shaft of an engine to a manualtransmission, includes a torque converter main body having a frontcover, the torque converter main body and the front cover defining ahydraulic oil chamber, an impeller fixed to the front cover within thehydraulic oil chamber, and a turbine disposed within the hydraulic oilchamber opposed to the impeller. A manual transmission input shaftextends into the hydraulic oil chamber. A disengaging clutch is disposedwithin the hydraulic oil chamber, the disengaging clutch mechanicallycoupled to the turbine and to the manual transmission input shaft, thedisengaging clutch configured to mechanically engage and disengage theturbine from the manual transmission input shaft. A lock-up clutch isdisposed within the hydraulic oil chamber, the lock-up clutch beingcoupled to the front cover and the manual transmission input shaft, thelock-up clutch configured to mechanically engage and dis-engage thefront cover from the manual transmission input shaft. A clutch operationmechanism at least partially disposed within the main body is configuredto shift between operation modes, the operation modes including a startmode, a drive mode and a speed change, wherein in the start mode thedisengaging clutch is engaged and the lock-up clutch is disengaged, inthe drive mode the lock-up clutch is engaged and in the speed changemode the disengaging clutch and the lock-up clutch are both disengaged.

Preferably, the disengaging clutch of the torque converter includes atleast one first output plate mechanically connected to the manualtransmission input shaft, a power input plate and a biasing cone spring.Further, it preferred to have the lock-up clutch have at least onesecond output plate mechanically connected to the manual transmissioninput shaft. The clutch operation mechanism includes a pressure platedisposed adjacent to the second output plate and a load applying plateis disposed between the first and second output plates. The biasing conespring urges the first output plate and the power input plate toward theload applying plate and the pressure plate is configured to engage aportion of the power input plate. The pressure plate is configured toengage the second power output plate for selective engagement anddisengagement of the lock-up clutch and selective engagement anddisengagement of the disengaging clutch.

In another aspect of the invention, the disengaging clutch preferablyincludes at least one first output plate mechanically connected to themanual transmission input shaft, a power input plate and a biasing conespring. The lock-up clutch includes at least one second output platemechanically connected to the manual transmission input shaft. Theclutch operation mechanism has a pressure plate disposed adjacent to thesecond output plate and a load applying plate disposed between the firstand second output plates. The biasing cone spring urges the first outputplate and the power input plate toward the load applying plate and thepressure plate is configured to engage the second power output plate forselective engagement and disengagement of the lock-up clutch. Further, acover plate disposed within the main body contacts the pressure platefor movement therewith, the cover plate being configured to engage aportion of the power input plate for selective engagement anddisengagement of the disengaging clutch.

In yet another aspect of the present invention the disengaging clutchhas at least one first output plate mechanically connected to the manualtransmission input shaft and a power input plate and a biasing conespring. The lock-up clutch includes at least one second output platemechanically connected to the manual transmission input shaft. Theclutch operation mechanism has a pressure plate disposed adjacent to thesecond output plate. Further, the biasing cone spring urges the firstoutput plate and the power input plate toward the turbine, and thepressure plate is configured to engage the second power output plate forselective engagement and disengagement of the lock-up clutch. The coverplate is disposed within the main body and is configured for movementwith the pressure plate, the cover plate being configured to engage aportion of the power input plate for selective engagement anddisengagement of the disengaging clutch.

In yet another aspect of the present invention, a pressure plate isurged by a diaphragm spring toward the disengaging clutch and thelock-up clutch. A hydraulic controller is in fluid communication withthe torque converter main body for controlling movement of the diaphragmspring, movement of the diaphragm spring being predetermined to definethe operation modes.

In still another aspect of the invention, a vibration dampeningmechanism is mechanically connected to the manual transmission inputshaft and the lock-up clutch.

In yet another aspect of the invention, a vibration dampening mechanismis mechanically connected to the turbine and the lock-up clutch.

In another configuration of the present invention, a torque converterfor transmitting torque from a crank shaft of an engine to a manualtransmission includes a torque converter main body having a front cover,an impeller fixed to the front cover, the front cover and the impellerdefining a hydraulic oil chamber, and a turbine disposed adjacent to theimpeller within the hydraulic oil chamber. A disengaging clutch disposedbetween the turbine and a manual transmission input shaft which extendsinto the main body. A lock-up clutch mechanically is coupled to thefront cover. A vibration dampening mechanism couples the disengagingclutch and the lock-up clutch in circular directions. A clutch operatingmechanism is configured to selectively engage and disengage thedisengaging clutch and the lock-up clutch in a plurality of shiftingmodes, the shifting modes including: a start mode where the disengagingclutch is engaged and the lock-up clutch is disengaged; a drive modewhere the disengaging clutch and the lock-up clutch are engaged, and aspeed change mode where the disengaging clutch is disengaged.

Preferably the clutch operating mechanism includes a shift elementengaging both the disengaging clutch and the lock-up clutch, a firstbiasing element urging the shift element toward both the disengagingclutch and the lock-up clutch, and an operating element for selectivelymoving the first pushing element. The disengaging clutch has a pluralityof first plate elements and a second biasing element urging the firstplate elements against each other, the second biasing element beingconfigured to urge the first plate elements into contact with oneanother in response to movement of the first biasing element. Further,the lock-up clutch includes a plurality of second plate elements, thesecond plate elements being urged into contact with one another inresponse to movement of the first urging element.

Preferably, the torque converter includes a supporting elementsupporting the first urging element and contacting the first urgingelement.

In the torque converter of the present invention, when the clutchoperating mechanism enters the start mode, the disengaging clutch isengaged while the lock-up clutch is disengaged. As a result, the torquetransmitted from the power input front cover to the impeller istransmitted by fluid pressure to the turbine and further transmitted tothe manual transmission through the disengaging clutch and the poweroutput mechanism. As a result, the vehicle to starts to more smoothlythan the prior art manual transmissions with only clutch for engagementand disengagement.

When the clutch operating mechanism enters the drive mode, the lock-upclutch is engaged. Thus, the torque in the power input front cover istransmitted directly to the power output mechanism through the lock-upclutch and is transmitted to the manual transmission. In this situation,since the torque of the power input front cover is mechanicallytransmitted to the manual transmission, the vehicle runs with improvedfuel economy.

When the clutch operating mechanism enters the speed change mode, thedisengaging clutch and the lock-up clutch are disengaged. Consequently,the torque of the power input front cover is not transmitted toward themanual transmission. In this situation, the driver can change gears inthe manual transmission.

In this torque converter, the single clutch operating mechanism permitssimultaneous operation of both the disengaging clutch and the lock-upclutch. Hence, an inner configuration of the torque converter is greatlysimplified.

In the event that the power output element includes an elastic element,torsional vibration is absorbed when the torque is applied toward themanual transmission.

In the torque converter in accordance with the present invention, whenthe clutch operating mechanism is put into the start mode, thedisengaging clutch is engaged while the lock-up clutch is disengaged. Asa result, torque transmitted to the power input front cover and theimpeller is transmitted via fluid movement to the turbine and furthertransmitted to the disengaging clutch and to the manual transmissioninput shaft. In this situation, fluid transmission of torque enables thevehicle to start moving smoothly.

When the clutch operating mechanism switches to the drive mode, thedisengaging clutch and the lock-up clutch are both engaged.Consequently, the torque of the power input front cover is transmittedto the manual transmission through the lock-up clutch, the elasticcoupling mechanism and the disengaging clutch. In this situation, sincethe torque from the power input front cover is mechanically transmittedto the manual transmission input shaft, the vehicle operates withgreater fuel efficiency. Further, the torque converter may be definedhas having two sections, a power input mechanism and a power outputmechanism, where the boundary between the two mechanisms is an elasticcoupling element or spring element which absorbs vibration between thepower input mechanism and the power output mechanism. In such a torquetransmission mechanism, the turbine and its peripheral elements arecomponents of the power output mechanism. Hence, a ratio of moment ofinertia of the power output mechanism to the moment of inertia of thepower input mechanism is increased compared with the prior artconfigurations. As a result, resonance frequency of the torque converterof the present invention is decreased to the idle revolution of theengine or under, and thus, occurrence of abnormal sound like clatteringsounds and internal indistinct sound is reduced while the vehicle runsunder normal operating conditions.

When the clutch operating mechanism enters the speed change mode, thedisengaging clutch is disengaged. Consequently, the torque of the powerinput front cover is no longer transmitted to the manual transmissioninput shaft. In this situation, the driver can change gears manually.

In such a torque converter, the single clutch operating mechanismpermits simultaneous operation of both the disengaging clutch and thelock-up clutch. Thus, an inner configuration of the torque converter isgreatly simplified.

In another aspect of the present invention, a lock-up clutch of a torqueconverter includes a main body, an impeller fixed to an inner surface ofthe main body, a turbine mounted within the main body adjacent to theimpeller for rotation with respect to the impeller, a lock-up clutchmechanism connected to the turbine for rotation therewith, and anundulated plate spring engageable with the lock-up clutch mechanism forabsorbing vibration in response to engagement of the lock-up clutchmechanism.

Preferably, the lock-up clutch includes a piston element selectivelyengageable and disengagable with a front cover of the main body and theundulated plate spring is disposed between the piston element andturbine, allowing limited angular displacement therebetween.

Preferably, the undulated plate spring is disposed within a viscousfluid charged chamber formed on the piston element.

Preferably, the undulated plate spring is disposed within a viscousfluid charged chamber formed on a front cover of the main body.

Preferably, the undulated plate spring is formed with a plurality ofarcuate portions and a plurality of lever portions which alternate andare unitarily formed, and alternating pairs of the lever portions areprovided with a hole for viscous fluid passage.

Preferably, the lock-up clutch further includes a weight elementdisposed between a front cover of the main body and the turbine, apiston element coupled to the turbine, the piston element configured forcoupling and uncoupling from the weight element, a hydraulic pressurecontrol device controlling hydraulic pressure within the main body forcontrolling coupling and uncoupling of the piston element from theweight element, and the undulated plate spring elastically coupling theweight element with the front cover in circular directions.

In still another aspect of the present invention, the lock-up clutchincludes a main body, an impeller fixed to an inner surface of the mainbody, a turbine mounted within the main body adjacent to the impellerfor rotation with respect to the impeller, a lock-up clutch mechanismconnected to the turbine, a spring coupled to the lock-up clutchmechanism for absorbing vibration in response to engagement of thelock-up clutch mechanism, a weight element disposed between a frontcover of the main body and the turbine, a piston element coupled to theturbine, the piston element configured for coupling and uncoupling fromthe weight element, a hydraulic pressure control device controllinghydraulic pressure within the main body for controlling coupling anduncoupling of the piston element from the weight element, and the springelastically coupling the weight element with the front cover in circulardirections.

Preferably, the spring is a coil spring.

However, it is more preferable for the spring to be an elongatedundulated spring.

In the lock-up clutch according to the present invention, torque fromthe front cover is transmitted to the power output element through theundulated plate spring. Since the undulated plate spring is downsized inwidth compared with the coil spring, the lock-up clutch as a whole canbe downsized in axial directions.

In the event that the torque converter further includes the pistonelement and the power output plate, torque transmission is selectivelyperformed since engagement and disengagement of the piston elementallows the piston element to be in selective contact with the frontcover, the torque is transmitted to the power output element through thepiston element, the undulated plate spring and the power output platewhen the piston element is in contact with the front cover.

In the event that the torque converter further includes the viscousfluid charged chamber, since the undulated plate spring is compressedwithin the viscous fluid charged chamber, compression of the undulatedplate spring causes viscous fluid to pass through a clearance gapbetween the undulated plate spring and the viscous fluid chargedchamber, and a specified level of viscous resistance is developed. Thus,the viscous fluid charged chamber and the undulated plate springimplement functions performed by both an elastic coupling mechanism anda friction resistance generating mechanism in the prior art, and theresultant device is further downsized.

In the event that the undulated plate spring is provided in part with ahole through which the viscous fluid can pass, the viscous fluid in aclosed space defined by the viscous fluid charged chamber and theundulated plate spring flows out through the hole when the undulatedplate spring is contracted. Hence, the undulated plate spring, whencontracted, is prevented from being deformed in radial directions, andthe closed space can be retained. Thus, the clearance gap between theundulated plate spring and the viscous fluid charged chamber can beretained at a predetermined distance, and a high level of viscousresistance can be attained.

In the event that the torque converter includes a weight element, pistonelement, and a hydraulic pressure control device, torque transmissionvia the lock-up clutch is disengaged while the piston element isdetached from the weight element because of hydraulic pressure controlwithin the torque converter by the hydraulic pressure control device. Inthis situation, since the weight element is coupled to the front coverthrough the elastic element, it functions as a dynamic damper toeffectively dampen vibration of the front cover and its peripherals.When the piston element is coupled to the weight element because of thehydraulic pressure control within the torque converter by the hydraulicpressure control device, torque of the front cover is transmitted to thepower output element through the undulated plate spring, the weightelement and the piston element. Torsional vibration transmitted from thefront cover and its peripherals can be dampened by contraction of theundulated plate spring in circular directions. Especially, since theweight element causes a ratio of moment of inertia of a power outputmechanism to a power input mechanism to be increased when the lock-upclutch is engaged, resonance frequency is reduced to the idle speed ofthe engine or lower in a power transmission system including the torqueconverter. This is useful to reduce the occurrence of abnormal soundlike clattering sound and internal indistinct sound. In such a lock-upclutch, since the hydraulic pressure control enables the lock-up clutchto be engaged and disengaged and the weight element to be coupled andreleased, accurate control is attained.

In the event that the torque converter further includes a weightelement, a piston element, a power output plate and the hydraulicpressure control device, when the hydraulic pressure control devicecontrols hydraulic pressure within the torque converter, the pistonelement moves in axial directions and may be engaged with or disengagedfrom the power output plate. When disengaged, the weight element is notcoupled to either of the power input or output mechanism. When thepiston element is engaged by hydraulic pressure control within thetorque converter by the hydraulic pressure control device, the poweroutput plate is held by and between the weight element and the pistonelement. As a result, torque of the front cover is transmitted to thepower output plate through the elastic element and then is applied tothe power output element. Under the condition, the weight element causesa ratio of moment of inertia or the power output mechanism to the powerinput mechanism to be increased. In consequence, resonance frequency canbe reduced to the idle speed of the engine or under in a powertransmission system including the torque converter, and this reduces theoccurrence of abnormal sound like clattering sound and internalindistinct sound in the transmission.

In the event that the torque converter further includes a weightelement, an elastic element, a piston element and a power output plate,the lock-up clutch does not transmit torque when the piston element isdetached from the power output plate. In this situation, the weightelement functions as a dynamic damper against the front cover with theelastic element intervening between them. This allows vibration in theengine to be dampened. When the hydraulic pressure control devicecontrols hydraulic pressure within the torque converter, the pistonelement moves in axial directions, and the power output plate is held byand between the piston element and the weight element. This results intorque being transmitted in parallel from the elastic element and theundulated plate spring to the power output plate. Under the condition,the weight element functions as part of a power output mechanism.Specifically, when the clutch is engaged, a ratio of moment of inertiaof the power output mechanism to moment of inertia of a power inputmechanism becomes greater, and consequently, resonance frequency shiftsto a low revolution area, so that occurrence of abnormal sound likeinternal indistinct sound in the transmission is reduced.

In yet another aspect of the present invention, a lock-up clutch of atorque converter for transmitting torque includes a main body having afront cover and an impeller formed on an inner surface thereof, aturbine mounted for rotation within the main body adjacent to theimpeller, a weight element disposed between the front cover and theturbine for rotation with respect to the front cover, an elastic elementcoupling the weight element with the front cover such that the weightelement has limited angular displacement with respect to the frontcover, a power output element connected to the turbine, a piston elementmounted for rotation with the front cover and configured for axialmovement with respect to the front cover, the piston element extendingbetween the power output element and the turbine, and a hydraulicpressure control device controlling hydraulic pressure within at leasttwo annular portions of the main body, the piston being moveable inaxial directions in response to control of hydraulic pressure, theweight element being engageable and disengagable from the piston elementin response to movement of the piston element.

Preferably, the elastic element is an elongated undulated spring.

Preferably, the elongated undulated spring is disposed in a viscousfluid charged chamber formed on the piston element.

Preferably, the undulated plate spring is formed with a plurality ofholes through which viscous fluid passes.

Preferably, the elongated undulated spring includes a plurality ofarcuate elements and a plurality of lever elements formed unitarily andalternating.

However, the elastic element may also be a coil spring.

In yet another aspect of the present invention a lock-up clutch of atorque converter for transmitting torque, includes a main body having afront cover and an impeller formed on an inner surface thereof, aturbine mounted for rotation within the main body adjacent to theimpeller, a weight element disposed between the front cover and theturbine, a piston element coupled to the weight element for rotationtherewith but configured for axial movement with respect to the weight,an elastic element elastically coupling the piston element with thefront cover allowing limited rotary displacement between the pistonelement and the front cover, a power output plate extending between theweight element and the piston element and coupled to the turbine, and ahydraulic pressure control device for controlling hydraulic pressurewithin the torque converter, the piston element moving axially inresponse to changes in hydraulic pressure.

The elastic element may be a coil spring.

In the lock-up clutch according to the present invention, torquetransmission by the lock-up clutch is disengaged when the piston elementis disengaged from the weight element because of hydraulic pressurecontrol within the torque converter by the hydraulic pressure controldevice. In this situation, since the weight element is coupled to thefront cover through the elastic element, it functions as a dynamicdamper to dampen vibration in the front cover and its peripheralcomponents.

When the hydraulic pressure control within the torque converter by thehydraulic pressure control device causes the piston element to becoupled to the weight element, torque of the front cover is transmittedto the power output element through the elastic element, the weightelement and the piston. Torsional vibration transmitted from the frontcover is dampened by compression in circular directions of the elasticelement. Since especially the weight element causes a ratio of moment ofinertia of the power output mechanism to moment of inertia of the powerinput mechanism to increase while the lock-up clutch is engaged,resonance frequency is reduced to the idle speed of the engine or underin a power transmission system including the torque converter. Thisreduces the occurrence of abnormal sound like clattering sound andinternal indistinct sound developed in the transmission.

In such a lock-up clutch, since the hydraulic pressure control allowsthe lock-up clutch to be engaged and disengaged and the weight elementto be coupled and released, accurate control can be attained.

In the lock-up clutch of the present invention, when hydraulic pressurecontrol within the torque converter by the hydraulic pressure controldevice causes the piston element to be released from the weight element,torque transmission by the lock-up clutch is disengaged. In thissituation, since the weight element is coupled to the front coverthrough the elastic element, it functions as a dynamic damper toeffectively dampen vibration in the front cover and its peripheralcomponents.

When the hydraulic pressure control within the torque converter by thehydraulic pressure control device allows the piston element to press thepower output plate against the weight element, torque of the front coveris transmitted to the power output element through the elastic element,the piston, and the power output plate. Torsional vibration transmittedfrom the front cover is dampened by compression in the circulardirections of the elastic element. Since especially the weight elementcauses a ratio of moment of inertia of the power output mechanism toincrease while the lock-up clutch is engaged, resonance frequency isreduced to the idle speed of the engine or under in a power transmissionsystem including the torque converter. Consequently, this is effectiveto avoid occurrence of abnormal sound like internal indistinct sound andclattering sound developed in the transmission.

In such a lock-up clutch, since the torque transmission is performed onopposite sides of the power output plate, surface pressure is reduced ifcapacities of the torque transmission are the same, and abrasion of thepower output plate is prevented to some extent.

In the event that the second elastic element is formed of a undulatedplate spring, the undulated plate spring can be diminished in widthcompared with the coil spring, and therefore, the look-up clutch as awhole can be downsized in axial directions.

In the event that the torque converter further includes a viscous fluidcharged chamber, since the undulated plate spring compresses within theviscous fluid charged chamber, compression of the undulated plate springcauses viscous fluid to pass through a clearance gap between theundulated plate spring and the viscous fluid charged chamber, and aspecified level of viscous resistance is developed. Thus, the viscousfluid charged chamber and the undulated plate spring can implementfunctions of both an elastic coupling mechanism and a frictionresistance generating mechanism in the prior art, and therefore, theresultant device can be further downsized with a possible reduction inthe number of parts.

In the event that the undulated plate spring is provided in part with ahole through which the viscous fluid can pass, when the undulated platespring is compressed, the viscous fluid in a closed space defined by andbetween the viscous fluid charged chamber and the undulated plate springflows out through the hole. Hence, the undulated plate spring isprevented from being transformed in radial directions when contracted,and the closed space can be retained. Thus, a predetermined clearancegap defined by and between portions of the undulated plate spring andthe viscous fluid charged chamber can be retained as it ispredetermined, and a greater level of viscous resistance can beobtained.

In accordance with yet another aspect of the present invention a lock-upclutch of a torque converter for transmitting torque includes a mainbody having a front cover and an impeller formed on an inner surfacethereof, a turbine mounted for rotation within the main body adjacent tothe impeller, a weight element disposed between the front cover and theturbine, the weight configured for rotation with respect to the frontcover, a friction disc element connected to the turbine for rotationtherewith, a piston element supported on the friction disc element forrotation with respect thereto, the piston element being moveable axiallywith respect to the disc element, an elastic element coupling the pistonelement with the front cover in circular directions, and a hydraulicpressure control device for controlling hydraulic pressure within thetorque converter, the piston element moveable in axial directions inresponse to hydraulic pressure changes to engage and disengage thefriction disc element and the weight.

Preferably, the elastic element is formed of a undulated ribbon-likeplate spring.

Preferably, a viscous fluid charged chamber is formed on the piston, theundulated ribbon-like plate spring being disposed therein.

Preferably, a portion of the undulated ribbon-like plate spring isprovided with a hole through which viscous fluid passes.

Preferably, the undulated ribbon-like plate spring includes a pluralityof arcuate elements and lever elements formed unitarily in alternatingsuccession.

In a lock-up clutch according to the present invention, when a hydraulicpressure control device controls hydraulic pressure within a torqueconverter, the piston element is moved in axial directions and isdisengaged from a power output plate. In this situation, a weightelement is coupled to neither a power input mechanism nor a power outputmechanism, as defined above.

When hydraulic pressure control within the torque converter by thehydraulic pressure control device causes the piston element to move inaxial directions, the power output plate is held by and between theweight element and the piston element. Consequently, torque of the frontcover is transmitted to the power output plate through an elasticelement and further applied to a power output element. In thissituation, the weight element increases a ratio of moment of inertia ofthe power output mechanism to a moment of inertia of the power inputmechanism. As a result, resonance frequency in a power transmissionsystem including the torque converter can be reduced to the idle speedof an engine or under, and this is useful for reducing occurrence ofabnormal sound like clattering sound and internal indistinct sound inthe transmission.

Since, especially in this lock-up clutch, the hydraulic pressure controlpermits the lock-up clutch to be engaged and disengaged and the weightelement to be coupled and released, accurate control can be performed.

In the event that the second elastic element is formed of a undulatedribbon-like plate spring, since the undulated ribbon-like plate springcan be downsized in width compared with a coil spring, the lock-upclutch as a whole can be downsized in axial directions.

In the event that the torque converter further includes a viscous fluidcharged chamber, the undulated ribbon-like plate spring expands andcontracts within the viscous fluid charged chamber, contraction of theundulated ribbon-like plate spring causes viscous fluid to pass througha predetermined clearance gap between the undulated ribbon-like platespring and the viscous fluid charged chamber, and a specified level ofviscous resistance is developed. The viscous fluid charged chamber andthe undulated ribbon-like plate spring can implement functions of bothan elastic coupling mechanism and a friction resistance generatingmechanism common to prior art configurations, and the resultant torqueconverter can be further downsized with a possible reduction in thenumber of parts.

In the event that the undulated ribbon-like plate spring is provided inpart with a hole through which viscous fluid can pass, the viscous fluidin a closed space defined by and between the viscous fluid chargedchamber and the undulated ribbon-like plate spring flows out through thehole when the undulated ribbon-like plate spring is contracted. Thisprevents the undulated ribbon-like plate spring from being transformedin radial directions while the undulated ribbon-like plate spring iscontracted, and the closed space can be retained. Thus, the clearancegap between the undulated ribbon-like plate spring and the viscous fluidcharged chamber can be retained as it is predetermined, and a largerlevel of viscous resistance can be obtained.

In accordance with another aspect of the present invention, a lock-upclutch of a torque converter for transmitting torque includes a mainbody having a front cover and an impeller formed on an inner surfacethereof, a turbine mounted for rotation within the main body adjacent tothe impeller, a weight element disposed between the front cover and theturbine, a first elastic element coupling the weight element with thefront cover allowing limited angular displacement between the weightelement and the first elastic element, a piston element disposedadjacent to the weight element configured for axial movement within themain body, a power output plate placed between the piston element andthe weight element, the power output plate coupled to a manualtransmission input shaft, a second elastic element between the pistonelement and the front cover allowing limited angular displacementtherebetween, and a hydraulic pressure control device controllinghydraulic pressure within the main body, the piston element beingmoveable in axial directions in response to changes in hydraulicpressure within the main body.

Preferably, the second elastic element is formed of an undulatedribbon-like plate spring.

Preferably, the piston element further includes a viscous fluid chargedchamber which houses the undulated ribbon-like plate spring.

Preferably, a portion of the undulated ribbon-like plate spring isprovided with a hole through which viscous fluid may pass.

Preferably, the undulated ribbon-like plate spring is includes aplurality of spring elements connected in series, each of the springelements having an arcuate portion and a pair of levers extending fromends the arcuate portion.

However, the second elastic element might also be a coil spring.

In a lock-up clutch of a torque converter according to the presentinvention, when a piston element is released from a power output plate,the lock-up clutch no longer transmit torque. In this situation, aweight element functions as a dynamic damper against the front coverthrough the first elastic element to dampen vibration in the engine.

When a hydraulic pressure control device controls hydraulic pressurewithin the torque converter, the piston element moves in axialdirections, so that the power output plate is held by and between thepiston element and the weight element. This permits torque to betransmitted in parallel from the first and second elastic elements tothe power Output plate. Under this condition, the weight elementfunctions as part of a power output mechanism. Specifically, duringengagement of the clutch, a ratio of moment of inertia of the poweroutput mechanism to moment of inertia of a power input mechanism isincreased. In consequence, resonance frequency shifts to a region of lowrevolution speed, and occurrence of abnormal sound like internalindistinct sound in the transmission is reduced.

In this lock-up clutch, the piston element is moved in axial directionsby the hydraulic pressure control device, and therefore, accuratecontrol can be performed.

In the event that the second elastic element is formed of a undulatedribbon-like plate spring, since the undulated ribbon-like plate springcan be downsized in width compared with a coil spring, the lock-upclutch as a whole can be downsized in axial directions.

In the event that the torque converter further includes a viscous fluidcharged chamber, since the undulated ribbon-like plate spring iscompressed within the viscous fluid chamber, contraction of theundulated ribbon-like plate spring causes the viscous fluid to passthrough a gap defined by and between the undulated ribbon-like platespring and the viscous fluid chamber, so that a certain level of viscousresistance is developed. Thus, the viscous fluid chamber and theundulated ribbon-like plate spring can implement functions of both anelastic coupling mechanism and a friction resistance generatingmechanism. The elastic coupling mechanism and friction resistancegenerating mechanism are common in the prior art prior artconfigurations. As a result present invention configuration, theresultant torque converter can be further downsized.

In the event that the undulated ribbon-like plate spring is provided inpart with a hole through which the viscous fluid can pass, the viscousfluid in a closed space defined between the viscous fluid chargedchamber and the undulated ribbon-like plate spring flows out through thehole when the curved plate spring is contracted. This prevents theundulated ribbon-like plate spring from being transformed in radialdirections when the undulated ribbon-like plate spring is contracted,and the closed space can be retained. Thus, the gap between theundulated ribbon-like plate spring and the viscous fluid charged chambercan be retained as it is predetermined, and a greater level of viscousresistance can be obtained.

These and other objects, features, aspects and advantages of the presentinvention will become more fully apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings where like reference numerals denote correspondingparts throughout, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary schematic side view showing some of the internalcomponents a torque converter in accordance with a first embodiment ofthe present invention;

FIG. 2 is a schematic side view similar to FIG. 1, of a torque converterin accordance with a second embodiment of the present invention;

FIG. 3 is a schematic side view similar to FIG. 1, of a torque converterin accordance with a third embodiment of the present invention;

FIG. 4 is a schematic side view similar to FIG. 1, of a torque converterin accordance with a fourth embodiment of the present invention;

FIG. 5 is a schematic side view similar to FIG. 1, of a torque converterin accordance with a fifth embodiment of the present invention;

FIG. 6 is a force diagram showing a dynamic model of the torqueconverter depicted in FIG. 5;

FIG. 7 is a schematic side view similar to FIG. 1, of a torque converterin accordance with a sixth embodiment of the present invention;

FIG. 8 is a fragmentary side sectional view of a torque converter inaccordance with a seventh embodiment of the present invention;

FIG. 9 is a schematic view of a hydraulic fluid control systemassociated with the torque converter depicted in FIG. 8, showing onefluid flow state;

FIG. 10 is a schematic view of the hydraulic fluid control systemdepicted in FIG. 9, showing a second fluid flow state;

FIG. 11 is a fragmentary, part section, front view of an undulatedribbon like spring employed in the torque converter depicted in FIG. 8,shown removed from the torque converter;

FIG. 12 a fragmentary, part section, front view of the undulated ribbonlike spring depicted in FIG. 11, shown within a chamber formed withinthe torque converter depicted in FIG. 8;

FIG. 13 force diagram showing a dynamic model of the torque converterdepicted in FIG. 8;

FIG. 14 a schematic side view similar to FIG. 1, of a torque converterin accordance with a eighth embodiment of the present invention;

FIG. 15 force diagram showing a dynamic model of the torque converterdepicted in FIG. 14;

FIG. 16 a schematic side view similar to FIG. 1, of a torque converterin accordance with a ninth embodiment of the present invention;

FIG. 17 a schematic side view similar to FIG. 1, of a torque converterin accordance with a tenth embodiment of the present invention;

FIG. 18 a schematic side view similar to FIG. 1, of a torque converterin accordance with a eleventh embodiment of the present invention;

FIG. 19 a schematic side view similar to FIG. 1, of a torque converterin accordance with a twelfth embodiment of the present invention;

FIG. 20 is a force diagram showing a dynamic model of the torqueconverter depicted in FIG. 19;

FIG. 21 a schematic side view similar to FIG. 1, of a torque converterin accordance with a thirteenth embodiment of the present invention;

FIG. 22 a schematic side view similar to FIG. 1, of a torque converterin accordance with a fourteenth embodiment of the present invention;

FIG. 23 is a force diagram showing a dynamic model of the torqueconverter depicted in FIG. 22;

FIG. 24 a schematic side view similar to FIG. 1, of a torque converterin accordance with a fifteenth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Embodiment 1

FIG. 1 is a schematic side view showing a torque converter 1a in a firstembodiment of the present invention. The torque converter 1a is amechanism for transmitting torque from a flexible plate 2 coupled to acrank shaft (not shown) in an engine (not shown) to a main drive shaft 3of a manual transmission (not shown). The engine is positioned to theleft in FIG. 1, while the manual transmission is positioned to the rightin FIG. 1.

The torque converter 1a primarily includes a front cover 4, a torqueconverter main body 5, a disengaging clutch 7, a lock-up clutch 8, anelastic coupling mechanism 9 and a hydraulic operating device 10.

The front cover 4 is fixed to the flexible plate 2.

The torque converter main body 5 includes three types of turbineelements, namely, an impeller 13, a turbine 14 and a stator 15. Theimpeller 13 is fixed to an outer circumferential tubular portion 4a ofthe front cover 4 and defines a hydraulic oil chamber along with thefront cover 4. The turbine 14 is positioned opposite to the impeller 13within the hydraulic oil chamber. The turbine 14 is rotatably supportedby the main drive shaft 3 through a first bearing 16. The stator 15 isplaced between inner circumferences of the impeller 13 and the turbine14 and is supported by a fixed shaft 18 via a one-way clutch mechanism17. The impeller 13 is also rotatably supported on the fixed shaft 18through a second bearing 19.

The disengaging clutch 7, the lock-up clutch 8, the elastic couplingmechanism 9 and the hydraulic operating device 10 are disposed in aspace defined between the front cover 4 and the turbine 14 within thehydraulic oil chamber of the torque converter 1a.

The disengaging clutch 7 is primarily includes a fixed element 21 fixedto a back surface of the turbine 14, a load applying plate 22, a firstpower output plate 23, a first power input plate 24 and a cone spring25. The fixed element 21 is a ring-shaped element and has its innercircumferential end fixed to the back surface of the turbine 14 and itsouter circumferential end having a cylindrical shape and referredhereinafter as a tube 21a which extends toward the front cover 2. Theload applying plate 22 engages the tube 21a so as to rotate therewithbut is confined so as not to move in axial directions relative to thetube 21a. The first power output plate 23, the first power input plate24 and the cone spring 25 are arranged in order between the fixedelement 21 and the load applying plate 22. The first power output plate23 has its inner circumferential end coupled to the elastic couplingmechanism 9, as described in greater detail below. The first power inputplate 24 has its outer circumferential end engaged with the tube 21a soas to rotate therewith but is able to move in axial directions withrespect to the tube 21a. Part of the first power input plate 24protrudes outward beyond the tube 21a through, for example, a slit (notshown) formed therein. The cone spring 25 is biased to urge the firstpower input plate 24 in a direction toward the flexible plate 2.

The lock-up clutch 8 primarily includes the load applying plate 22 and asecond power output plate 27. The second power output plate 27 ispositioned adjacent to the load applying plate 22 as shown in FIG. 1,and has its inner circumferential end coupled to the elastic couplingmechanism 9.

The elastic coupling mechanism 9 includes an engaging plate 31, asupporting plate 32, a power output plate 33 and a plurality of coilsprings 34. The engaging plate 31 is provided with a tubular portion 31ain its outer circumferential portion, and inner circumferential portionsof the first power output plate 23 and second power output plate 27engage with the tubular portion 31a so as to rotate therewith but isable to move in axial directions relative to the tubular portion 31a.The engaging plate 31 and the supporting plate 32 are opposed to eachother in axial directions, and an outer circumferential portion of thepower output plate 33 is positioned between the plates 31 and 32. Theengaging plate 31, the supporting plate 32 and the power output plate 33are elastically coupled to one another in circular directions throughcoil springs 34. The power output plate 33 has its inner circumferentialend in spline engagement with the main drive shaft 3.

The hydraulic operating device 10 primarily includes a pressure plate28, a diaphragm spring 36, a release bearing 37 and a hydraulicoperating chamber 38. The pressure plate 28 is positioned adjacent tothe second power output plate 27 close to the front cover 2 and providedwith an annular projecting portion 28a on an opposite side from thesecond power output plate 27.

The pressure plate 28 has its outer circumferential portion fixed to theouter circumferential tubular portion 4a of the front cover 4 by, forinstance, strap plates (not shown) so as to rotate therewith but is ableto move in axial directions, The pressure plate 28 is urged toward theengine by the strap plates (not shown). In an outer circumferentialportion of the pressure plate 28, a pusher 28b is formed which isaxially aligned with the part of the first power input plate 24 whichprotrudes beyond the tube 21a. The diaphragm spring 36 has its outercircumferential end supported by an annular supporting portion 4b formedin the front cover 4. The intermediate portion in radial directions ofthe spring 36 engages and urges the projecting portion 28a of thepressure plate 28 toward the turbine 14. The release bearing 37 ispositioned at an inner circumferential end of the diaphragm spring 36.The release bearing 37 is fixed to a moveable portion extending from thehydraulic operating chamber 38. Hydraulic pressure within the hydraulicoperating chamber 38 is controlled by a hydraulic operating circuit 100.

The operation of the torque converter will now be described.

Start Mode

In a start-up mode, hydraulic oil pressure in the hydraulic operatingchamber 38 is controlled by the hydraulic circuit 100 to move therelease bearing 37 to a position close to the front cover 4. Themovement of the release bearing 37 causes an inner circumferential endof the diaphragm spring 36 to move toward the front cover 4 to releasethe pressure plate 29 from the urging force exerted by the diaphragmspring 36. In this situation, the pressure plate 28 is urged by thestrap plates (not shown) to a first position close to the front cover 4.In this condition, a clearance gap A is established between the pusher28b of the pressure plate 28 and the outer circumferential portion ofthe first power input plate 24 causing the disengaging clutch 7 to beengaged. When the clearance gap A is established, the urging force ofthe cone spring 25 allows the first power output plate 23 and the firstpower input plate 24 to be in press-contact with the load applying plate22, and the turbine 4 and the elastic coupling mechanism 9 are coupledto each other. In the lock-up clutch 8, a clearance gap B is establishedbetween the pressure plate 28 and the second power output plate 27 whilea clearance gap C is established between the second power output plate27 and the load applying plate 22, and the lock-up clutch 8 isdisengaged. When the lock-up clutch 8 is disengaged, and the disengagingclutch 7 is engaged, the gaps A, B and C have the followingrelationship: B+C>A.

When the lock-up clutch 8 is disengaged, and the disengaging clutch 7 isengaged, torque from the crank shaft (not shown) is transmitted to thefront cover 4 through the flexible plate 2. The flexible plate 2 absorbsbending vibration of the torque. The impeller 13 rotates along with thefront cover 4, the hydraulic oil within the torque converter main body 5flows from the impeller 13 toward the turbine 14, and the turbine 14rotates. The torque of the turbine 14 is transmitted to the elasticcoupling mechanism 9 through the disengaging clutch 7. The torque isapplied from the elastic coupling mechanism 9 to the main drive shaft 3and further transmitted to the manual transmission (not shown). Thetorsional vibration of the torque is dampened in the elastic couplingmechanism 9.

Hence, in the start mode, torque is transmitted primarily by fluidmovement in the torque converter main body 5 and the vehicle equippedwith the present invention starts moving smoothly in a manner similar tomovement in a vehicle equipped with an automatic transmission andcorresponding torque converter.

Drive Mode

In a drive mode, a predetermined level of hydraulic pressure is suppliedto the hydraulic operating chamber 38 from the hydraulic circuit 100 tomove the release bearing 37 to a drive mode position (not shown) wherethe diaphragm spring 36 moves to an intermediate position closer to theturbine 14 than in the start mode described above. In the drive modeposition, the diaphragm spring 36 pushes the pressure plate 28 towardthe turbine 14, the pusher 28b of the pressure plate 28 moves the outercircumferential portion of the first power input plate 24 against thepushing force of the cone spring 25, and the pressure plate 28 causesthe second power output plate 27 to be in press-contact with the loadapplying plate 22. Thus, the disengaging clutch 7 is disengaged and thelock-up clutch 8 is engaged. In this situation, the pushing force of thediaphragm spring 36 is transmitted to the turbine through the loadapplying plate 22 and the fixed element 21.

With the disengaging clutch 7 disengaged and the lock-up clutch 8engaged, torque from the front cover 4 is applied to the main driveshaft 3 through the lock-up clutch B and the elastic coupling mechanism9. In the drive mode, the torque from the front cover 4 is transmittedmechanically to the manual transmission (not shown) without the use ofthe torque converter main body 5, and hence, the vehicle runs withgreater fuel efficiency.

Speed Change Mode

In a speed change mode, a predetermined level of hydraulic pressure issupplied to the hydraulic operating chamber 38, and the release bearing37 is moved to a position between the start mode position and the drivemode position. This allows the inner circumferential end of thediaphragm spring 36 to move part way back toward the front cover 4 (butnot as far as the start mode position). In this situation, the pressureplate 29 is displaced toward the transmission by a distance D(A<D<(B+C)) from a position where it is in the start mode. It should benoted that the distance D is only defined but is not shown in thefigures. Under this condition, although the pusher 28b of the pressureplate 28 continues to cause the outer circumferential end of the firstpower input plate 24 to move slightly toward the turbine 14, a smallclearance gap is retained between the pressure plate 28 and the secondpower output plate 27 and the load applying plate 22; that is, both thelock-up clutch 8 and the disengaging clutch 7 are disengaged. In such acircumstance, the torque is not transmitted from the front cover 4 tothe main drive shaft 3, and the driver is able to change gears by usingthe manual transmission.

As has been described, the disengaging clutch 7 and the lock-up clutch 8are operated simultaneously by the hydraulic operating device 10. Thus,two of the clutches are actuated by a single operating mechanism. Thisleads to a greatly simplified inner configuration of the torqueconverter 1. As will be recognized in the drawing, the disengagingclutch 7 and the lock-up clutch B are disposed side by side close toeach other, and they are each engageable with load applying plate 22.Such an arrangement of the clutches disposed close to each othersimplifies a structure of the related portion and makes the wholestructure more compact.

Embodiment 2

FIG. 2 is a schematic sectional view showing a torque converter 1b in asecond embodiment of the present invention. Herein and in otherembodiments of the present invention described below, there variouscomponents and elements common to several of the various embodiments. Inorder to eliminate repetition, explanation of the some of the previouslydescribed elements is omitted, and generally, only differing orreconfigured elements will be described.

The torque converter 1b in this embodiment is generally configured in amanner similar to the torque converter 1a in Embodiment 1. However, thehydraulic operating device 10 in the second embodiment includes a coverplate 45 covering an outer circumferential portion of a diaphragm spring36 within the torque converter main body 5. The cover plate 45 has anannular supporter 45a supporting the outer circumferential portion ofthe diaphragm spring 36 close to the front cover 4. The cover plate 45has its outer circumferential portion fixed to a tubular outercircumferential portion 4a of the front cover 4. Moreover, the coverplate 45 has an engaging portion 45b in contact with an outercircumferential portion of the load applying plate 22 close to thetransmission. Thus, the cover plate 45 supports the outercircumferential portion of the diaphragm spring 36 and supports load inthe lock-up clutch 8 applied from the diaphragm spring 36. Thus, theload in the lock-up clutch 8 applied from the diaphragm spring 36 nolonger affect a turbine 14. As a consequence, the load applied to theturbine 14 is reduced compared to the first embodiment, and the load tothe first bearing 16 supporting the turbine 14 is accordingly reduced,so that the functional life of the first bearing 16 may be extended.

Embodiment 3

FIG. 3 is a schematic view showing a model of a torque converter 1c inaccordance with a third embodiment of the present invention.

In the third embodiment, the disengaging clutch 7 primarily includes afixed element 51, a first power input plate 52, a first power outputplate 53, a first load applying plate 54, a cone spring 55, and a secondload applying plate 56. The fixed element 51 is a ring-shaped elementfixed to an outer circumference of a turbine 14 and is provided in anouter circumference with a tube 51a extending toward the front cover 4.The first load applying plate 54 has its outer circumferential portionput in contact with a restraining portion 51b formed inside the tube 51aand is thereby restrained from moving toward the turbine 14. The secondload applying plate 56 is placed closer to the front cover 4 than thefirst load applying plate 54 and has its outer circumferential portionplaced between a pair of restraining portions 51c and 51d of the tube51a of the fixed element 51 so as to have limited movement in axialdirections therebetween. Between the first load applying plate 54 andthe second load applying plate 56, the first power output plate 53, thefirst power input plate 52 and the cone spring 55 are disposed in thisorder from a side close to the first load applying plate 54. The firstpower output plate 53 has its inner circumferential portion coupled tothe elastic coupling mechanism 9. The first power input plate 52 has itsouter circumferential portion engaged with the tube 51a so as to rotatetherewith but may move in axial directions relative thereto. The outercircumferential portion of the first power input plate 52 partiallyprotrudes outward beyond the tube 51a. The cone spring 55 is slightlycompressed in position to urge the first power input plate 52 toward theturbine 14.

The lock-up clutch 8 is primarily includes the second load applyingplate 56 and a second power output plate 57. The second power outputplate 57 is placed in the second load applying plate 56 close to theengine and has its inner circumferential portion engaged with theelastic coupling mechanism 9 so as to rotate therewith but may move inaxial directions via, for instance, slots (not shown).

The hydraulic operating device 10 includes a pressure plate 58, adiaphragm spring 36, a release bearing 37 and a hydraulic operatingchamber 38. The pressure plate 58 is positioned adjacent to the secondpower output plate 57 close to the engine. The pressure plate 58 has itsouter circumferential portion fixed to an outer circumferential tubularportion 4a of a front cover 4 through strap plates (not shown) so as torotate therewith but may move in axial directions. The strap plates (notshown) urge the pressure plate 58 toward the front cover 4. An outercircumferential end of the diaphragm spring 36 is engageable with anannular projecting portion 58a of the pressure plate 58. An intermediateportion in radial directions of the diaphragm spring 36 is supported byan annular supporter 4b of the front cover 4. The diaphragm spring 36has an inner circumferential end in contact with the release bearing 37.One end of the coupling plate 59 includes an inwardly extending portion59a which contacts and restrain an outer circumferential edge of thediaphragm spring 36 while the other end 59b of the coupling plate 59extend radially inwardly to be contactable with an outer circumferentialend of the first power input plate 52.

In a start mode, the release bearing 37 causes an inner circumferentialend of the diaphragm spring 36 to slightly move toward the turbine 14.Hence, the outer circumferential portion of the diaphragm spring 36slightly moves toward the front cover 4. Thus, the pressure plate 58 isreleased from pushing force by the diaphragm spring 36, and the pressureplate 58 is urged toward the front cover 4 by the strap plates (notshown). In this situation, although the coupling plate 59 slightly movestoward the front cover 4 as the outer circumferential end of thediaphragm spring 36 moves, the end 59b does not come in contact with theouter circumferential portion of the first power input plate 52. As aresult, the disengaging clutch 7 is engaged while the lock-up clutch 8is disengaged.

To a drive mode, the release bearing 37 moves toward the front cover 4in the drawing to release an inner circumferential end of the diaphragmspring 36 from the pushing force. Thus, the outer circumferentialportion of the diaphragm spring 36 moves toward the turbine 14 to pushthe pressure plate 58. In consequence, the disengaging clutch 7 and thelock-up clutch 8 are engaged,

In a speed change mode, the release bearing 37 moves to a positionclosest to the turbine 14 to move the inner circumferential end of thediaphragm spring 36 to a position closest to the turbine 14. Thisresults in releasing the pressure plate 58 from being urged againstsecond power output plate 57, and the lock-up clutch 8 is disengaged.The coupling plate 59 greatly moves toward the front cover 4 along withthe outer circumferential end of the diaphragm spring 36. As a result,the end 59b of the coupling plate 59 close to the turbine 14 urges theouter circumferential end of the first power input plate 52 toward thefront cover 4, and this, in turn, disengage the disengaging clutch 7.

Embodiment 4

FIG. 4 is a schematic sectional view showing a torque converter 1d inaccordance with a forth embodiment of the present invention. The torqueconverter 1 of this embodiment has a similar configuration to the torqueconverter 1c in Embodiment 3.

In the fourth embodiment, the hydraulic operating device 10 additionallyincludes a cover plate 61 covering an outer circumferential side of adiaphragm spring 36. The cover plate 61 is a ring-shaped element and hasits outer circumferential portion fixed to an outer circumferentialtubular portion 4a of a front cover 4. The cover plate 61 is formed witha tube 61a on its outer circumferential portion, the tube 61a extendingtoward the turbine 14, and an end of the tube 61a close to the turbine14 is bent inward to make an engaging portion 61b which comes in contactwith an outer circumferential portion of a first load applying plate 54close to the turbine 14. In an inner circumference of the cover plate61, an annular supporter 61c is formed for supporting an intermediateportion in radial directions of the diaphragm spring 36. In thisembodiment, since load of a cone spring 55 is received by the coverplate 61, load on the turbine 14 is reduced. Load on a first bearing 16supporting the turbine 14 is accordingly reduced, and the lifeexpectancy of the first bearing 16 is possibly extended.

Embodiment 5

FIG. 5 is a schematic sectional view showing a torque converter 1eaccording to a fifth embodiment of the present invention while FIG. 6 isa diagram showing a dynamic model of the same.

A fixed plate 67 is a disk-shaped element fixed to the turbine 14. Thefixed plate 67 has its outer circumferential portion bent inward to makea supporter 68 defining an annular space 68a. The fixed plate 67 isrotatably supported by a main drive shaft 3 through a first bearing 16.

A disengaging clutch 7 primarily includes an outer circumferentialportion of a power output plate 69 placed within the annular space 68a,a first power input plate 70, and a cone spring 71. An innercircumferential portion of the power output plate 69 is engaged inspline with the main drive shaft 3. Between the outer circumferentialportion of the power output plate 69 and the supporter 68, the firstpower input plate 70 and the cone spring 71 are disposed in order fromthe power output plate 69. An outer circumferential portion of the firstpower input plate 70 engages with a tubular portion of the supporter 68so as to rotate therewith but may move in axial directions. Part of theouter circumferential portion of the first power input plate 70protrudes outward beyond the tubular portion of the supporter 68. Thecone spring 71 is compressed in position to urge the first power inputplate 70 toward the turbine 14.

The lock-up clutch 8 consists of two second power input plates 64 and asecond power output plate 65. The second power input plates 64 areengaged with an outer circumferential tubular portion 4a of a frontcover 4 so as to move in axial directions in a predetermined range butnot to relatively rotate. An outer circumferential portion of the secondpower output plate 65 is positioned between the second power inputplates 64. An inner circumferential end of the power output plate 69 iselastically coupled in circular directions to the fixed plate 67 througha plurality of coil springs 34.

The hydraulic operating device 10 includes the diaphragm spring 36, therelease bearing 37, the hydraulic operating chamber 38 and the pressureplate 66. An outer circumferential end of the diaphragm spring 36 closeto the front cover 4 is supported by an annular supporter 4b of thefront cover 4, and its intermediate portion in radial directions comesin contact with an annular projection 66a of the pressure plate 66. Therelease bearing 37 is placed in an inner circumferential end of thediaphragm spring 36 close to the turbine 14. In an outer circumferenceof the pressure plate 66, there are formed a pusher 66b coming incontact with the second power input plate 64 and an engaging portion 66cplaced in an outer circumferential end of the first power input plate 70close to the turbine 14.

Hereinbelow, the torque converter 1e is defined as having two sections,a power input mechanism and a power output mechanism. The power inputmechanism is defined as including at least the front cover 4, theimpeller 13, and the lock up clutch 8. The power output mechanismincludes at least the turbine 14, the fixed plates 67 and thedisengaging clutch 7. The spring 34 divides the power input mechanismfrom the power output mechanism.

An operation of the torque converter will be described below.

In a start mode, the hydraulic circuit 100 controls the hydraulicpressure within the hydraulic operating chamber 38 to cause the releasebearing 37 to move toward the front cover 4 to cause the innercircumferential end of the diaphragm spring 36 to move accordingly. Inthis situation, although the pusher 66b of the pressure plate 66slightly pushes the second power input plate 64, the lock-up clutch 8becomes disengaged, and the disengaging clutch 7 is engaged because theengaging portion 66c does not come in contact with the first power inputplate 70. As a result, torque from the torque converter main body 5 isapplied to the main drive shaft 3 through the disengaging clutch 7.

In a drive mode, the release bearing 37 is moved toward the turbine 14to release the diaphragm spring 36 from the pushing force. This resultsin the diaphragm spring 36 pushing the pressure plate 66 toward theturbine 14. In such a position, the pusher 66b of the pressure plate 66causes the second power input plate 64 toward the turbine 14, so thatthe lock-up clutch 8 becomes engaged. In this situation, as shown inFIG. 6, in the power input mechanism and the power output mechanism aredivided by the coil springs 34 intervening between them, the turbine 14and the fixed plate 67 function as elements for the power outputmechanism. Specifically, in a torque transmitting system including thetorque converter 1, a ratio of moment of inertia of the power outputmechanism is sufficiently increased. Hence, resonance frequency isdecreased to the idle speed of the engine (not shown) or lower, andoccurrence of abnormal sound in the transmission (not shown) is reduced.

In a speed change mode, the release bearing 37 moves toward the frontcover 4 to cause the inner circumferential end of the diaphragm spring36 to accordingly move. In this situation, the pusher 66b of thepressure plate 66 is detached from the second power input plate 64, andthe engaging portion 66c causes the first power input plate 70 to movetoward the front cover 4. Thus, the disengaging clutch 7 and the lock-upclutch 8 become disengaged so as to change gears.

Embodiment 6

A torque converter 1f in accordance with a sixth embodiment of thepresent invention is shown in FIG. 7. The embodiment shown in FIG. 7 issimilar to the torque converter 1e in Embodiment 5. However, thehydraulic operating device 10 in the torque converter 1f, includes acover plate 75 covering an outer circumferential side of the diaphragmspring 36. The cover plate 75 is fixed to an outer circumferentialtubular portion of the front cover 4 and has an annular supporter 75asupporting an outer circumferential end of the diaphragm spring 36. Thecover plate 75 is further provided in an outer circumferential portion atube 75b extending in axial directions. Two second power input plates 64are engaged with the tube 75b so as to move in axial directions in aspecified range but not to relatively rotate. In this embodiment, sincepushing force by the diaphragm spring 36 is received by the cover plate75, load applied to a turbine 14 is reduced. Consequently, load appliedto the first bearing 16 supporting the turbine 14 is reduced, and itfunctional life may be extended.

Embodiment 7

FIG. 8 is a schematic sectional view showing a torque converter 1g in aseventh embodiment of the present invention.

The torque converter 1g primarily includes three types of turbineelements, an impeller 13, a turbine 14 and a stator 15. The impeller 13together with a front cover 102 coupled to the crank shaft (not shown)of an engine (not shown) constitutes a hydraulic oil chamber. Theturbine 14 is coupled to the main drive shaft 109 through a turbine hub108. The stator 15 is placed between an inner circumferential portion ofthe impeller 13 and a hub 108 attached to an inner circumferentialportion of the turbine 14.

A lock-up clutch 110 is placed in a space defined by and between thefront cover 102 and the turbine 14. The lock-up clutch 110 includes apiston 116, a plate element 119 defining a viscous fluid charged chamberalong with the piston 116, a pair of undulated plate springs 118disposed within the viscous fluid charged chamber, and a plate element131 fixed to the turbine hub 108.

The undulated plate springs 118 are elements for transmitting torqueapplied from the piston 116 to the plate element 131. The undulatedplate springs 118 are made of plate-like elements of a certain widthcontinually bent in longitudinal directions, as shown in FIG. 11, and inthis embodiment, two of the plate-like elements are used.

The viscous fluid charged chamber is confined within the piston 116 andthe plate element 119. The piston 116 is a disk-like element and has itsinner circumferential portion supported by the turbine hub 108 so as tobe rotatable and movable in axial directions. An annular frictionelement 116a is fixed to a surface of an outer circumferential portionof the piston 116 opposed to the front cover 102. Moreover, in the outercircumferential portion of the piston 116, a tube 116b protruding towardthe turbine 14 is formed. The plate element 19 is a disc-like elementplaced with a specified distance from the piston 116 and defines theviscous fluid charged chamber along with the piston 116. An outercircumferential portion of the plate element 119 is shaped to form atube 119a that is confined within an inner circumferential side of thetube 116b. A plate element 131 is a disc-like element and has its innercircumferential end fixed to the turbine hub 108 and its outercircumferential portion inserted in an inner circumference of theviscous fluid charged chamber. As shown in FIG. 12, the tube 119a of theplate element 119 is provided in two opposed positions with engagingportions 119b protruding inward toward one another. In an outercircumferential portion of the plate element 131, engaging portions 131aprotruding outward are formed in two opposed positions. The viscousfluid charged chamber is divided inside into two cells by the engagingportions 119b and 131a. The undulated plate springs 118 are respectivelydisposed in arc shape in the cells of the viscous fluid charged chamber.

The undulated plate springs 118 will be described in detail, referringto FIG. 11. As shown in FIG. 11, the undulated plate springs 18 are madeof a plurality of spring elements connected in series, which are made upof arc portions 120 and levers 121. The spring elements are connected toeach other by the levers 121 to form a continuous undulated spring.

The arc portions 120 are annular in shape with roughly the samediameter, and there is a given clearance gap S₁ between adjacent ones ofthe arc portions 120 when in a stress free state (shown in FIG. 11).Inside the arc portions 120, openings ends 123 are formed. The openingsends 123 have a clearance gap S₂ when they are under a free condition ora set condition, and the levers 121 extend outward from opposite sidesof each of the openings ends 123. The levers 121 extend so that adistance between them becomes larger as they go outward, and they arecontiguous to one of the levers 121 extending from opposite one of thearc portions 120.

A width of the undulated plate springs 18 are almost equal to that ofthe viscous fluid charged chamber, and its length in radial directionsis smaller than that of the viscous fluid charged chamber. When theundulated plate springs 118 are inserted into the viscous fluid chargedchamber, as shown in FIG. 12, there are a plurality of closed spaces 125defined between the tube 119a and the undulated plate springs 118. Inpart of the levers 121 of the undulated plate springs 118, holes 124 areformed to make hydraulic oil reserved in some of the closed spaces 125flow out. In this embodiment, the holes 124 are formed so that thehydraulic oil flows from every other ones of the closed spaces 125.

The arc portions 120 at outside opposite ends of the undulated platesprings 118 are engaged with the engaging portions 119b while the arcportions 120 at inside opposite ends are engaged with the engagingportions 131a. In such a configuration, the torque applied to the piston116 is transmitted to the plate element 131 through the undulated platesprings 118.

As is shown in FIG. 8, space I is formed between a back surface of theturbine 14 and the piston 116 while a space II is formed between thepiston 116 and the front cover 102. The friction element 116a is pressedat its outer circumferential portion by the front cover 102 to close thespace II. An inner circumferential portion of the space II is conductedto a third oil duct 148 (described in greater detail below) passingthrough the main drive shaft 109.

FIG. 9 depicts a hydraulic pressure control circuit 140 for controllinghydraulic pressure within the torque converter 1g. The hydraulic oil issupplied from a oil pump 141 to the torque converter 1g, a lock-upcontrol valve 143 and a lock-up solenoid 144 through a pressureregulator 142. A first oil duct 146 is a duct for supplying hydraulicoil from the pressure Iregulator 142 to the impeller 13. A second oilduct 147 is a duct for draining the hydraulic oil flowing from theturbine 14. The third oil duct 148 extends from the lock-up controlvalve 143, passing through the main drive shaft 109, and is conducted tothe space II within the torque converter 1g.

An operation of the torque converter will now be described.

In a state as shown in FIG. 9, the lock-up solenoid 144 is in adisengaged state, and the hydraulic oil drains from a drain X₂ of thelock-up solenoid 144. As a result, there is no hydraulic pressure in ahead of a piston of the lock-up control valve 143, and the piston ispushed to the right in FIG. 9 by force of a spring 143b to close a drainX₁. In this way, the lock-up control valve 143 leads the hydraulic oilfrom the pressure regulator 142 to the third oil duct 148. This causeshydraulic pressure to act in the space II within the torque converter1g, and this then causes the piston 116 to move to the right in FIG. 8.Under the condition, the friction element 116a is released from thefront cover 102; that is, the lock-up clutch 110 is disengaged.

When a speed of the vehicle reaches a specified level, the lock-upsolenoid 144 responds to a signal from a speed sensor (not shown) toturn on. Then, as shown in FIG. 10, the hydraulic pressure pushes thepiston of the lock-up control valve 143 to the left in FIG. 10, and thehydraulic oil within the space II of the torque converter 1g is drainedtherefrom through the third oil duct 148 and the lock-up control valve143. This causes the hydraulic pressure within the space II to becomelower than that in the space I, and consequently, the piston 116 movestoward the left in FIG. 8. In this situation, the friction element 116ais pressed against the front cover 102.

When torsional vibration is transmitted to the piston 116 while thelock-up clutch 110 is engaged, the undulated plate springs 118 arecompressed to dampen the torsional vibration. When the undulated platesprings 118 are compressed, an opening angle made by the levers 121becomes smaller, and bending moment affects the arc portions 120. Inthis situation, the levers 121 flex with fulcrums of the opening ends123. The bending moment is dispersed uniformly in longitudinaldirections in the levers 121, and elastic energy is separately stored bythe arc portions 120.

A torsional characteristic in this case depends upon torsional rigidityof the undulated plate springs 118. For example, in a range of a smalltorsional angle where the opening ends 123 have the clearance gap S₂,the arc portions 120 and the levers 121 flex in the same direction withfulcrums of an outer circumferential portions of the arc portions 120 ofthe undulated plate springs 118, and the torsional rigidity is small. Onthe other hand, when the torsional angle becomes larger, the clearancegap S₂ reaches zero, and the torsional rigidity is increased because theelastic energy is stored by the arc portions 120 with the fulcrums ofthe opening ends 123.

When the undulated plate springs 118 are compressed in the viscous fluidcharged chamber as mentioned before, the hydraulic oil passes through aclearance gap defined by the undulated plate springs 118 and the viscousfluid charged chamber, and viscous force produces vibration dampeningforce. This eftect will be explained below, referring to FIG. 12.

As illustrated in FIG. 12, no holes are formed in the levers 121defining the closed spaces 125 in a hatched region A in the closedspaces 125. Hence, when the undulated plate springs 118 are compressed,the hydraulic oil passes through a small gap between the undulated platesprings and the viscous fluid charged chamber, and a high level ofviscous resistance is developed. On the other hand, in another region Bin the closed spaces 125, the holes 124 are formed in the levers 121.Thus, the hydraulic oil flows through the holes 124, and the viscousresistance becomes small.

A model of the power transmission system which includes the hydraulicoil and the undulated plate spring 118 housed in the viscous fluidcharged chamber would be depicted in FIG. 13. Referring to FIG. 13, K1denotes a spring component made by the region B in FIG. 12 while K2 is aspring component made by the region A. C is a viscous resistancegenerating element made by the region A. In FIG. 13, viscous resistanceFc and spring force Fk are expressed as follows:

Fc=C·dθ/dt dθ/dt: rotation speed

Fk=K·θ θ: displacement of rotation angle

In the configuration as stated above, the spring force of the region Ais small and the viscous resistance in the same region is large becausenon-compressible viscous fluid is housed in the region A and alsobecause the clearance gaps are small therein. Thus, FC>>Fk2 is given.Hence, the spring component K2 in FIG. 13 may be ignored, and the springforce of the spring component K1 and the viscous resistance act inseries, and this is effective to reduce the resonance trequency.

If the undulated plate springs 118 are not provided in part with theholes 124, the undulated plate springs 118 are transformed inward so asto be released from the tube 119a since the hydraulic oil isnon-compressible. In such a case, expansion of the clearance gaps wherethe hydraulic oil passes prevents from attaining a desired level of theviscous resistance, and the power transmission system where the springforce and the viscous resistance act in series cannot be implemented.

In this embodiment as has been described, the undulated plate spring 118is used to downsize the torque converter in dimension in axialdirections, compared to the prior art employing coil springs. Inaddition to that, since the viscous fluid charged chamber and theundulated plate spring 118 develop both the elastic force and theviscous resistance, a very simple configuration attains effectivedampening of torsional vibration.

In the above-mentioned embodiment, although the space S₂ is retained inthe opening ends 123 in setting the undulated plate springs, the spaceS₂ of the openings 123 in the setting may be zero.

Embodiment 8

FIG. 14 is a schematic sectional view showing a torque converter 1h inan eighth preferred embodiment of the present invention while FIG. 15 isa view of a dynamic model of the same.

A lock-up clutch 210 is placed in a space between a front cover 202 anda turbine 14. The lock-up clutch 210 primarily includes an inertia plate211, a pair of undulated plate springs 218 placed within a viscous fluidcharged chamber 232a, which is defined within a disc-shaped plateelement 232, and a piston 216.

The inertia plate 211 is a disc-like element placed on a side of thefront cover 202. An inner circumferential end of the inertia plate 211is tubular in shape, protruding toward the transmission, and issupported by a thrust bearing 213 and a bush 214 so as to relativelyrotate to the front cover 202. In an outer circumference of the inertiaplate 211, an annular weight 211a is fixed. The inertia plate 211 iscoupled to the undulated plate springs 218 through a plate element 231.

The piston 216 is a disc-like element placed close to the turbine 14beside the inertia plate 211, and has its inner circuaferential endsupported by a turbine hub 20B through a bearing 219 so as to rotatewith the turbine hub 208 and engaged with the turbine hub 208 so as tomove in axial directions. In a surface opposed to the inertia plate 211in an cuter circumferential portion of the piston 216, an annularfriction element 216a is fixed.

In the above-mentioned configuration, a clutch 250 includes an outercircumferential portion of the inertia plate 211 and a friction element216a of the piston 216.

The disc-shaped plate element 232 fixed to the front cover 202 defines aviscous fluid charged chamber 232a. Within the viscous fluid chargedchamber, the undulated plate springs 218, similar to those as explainedin the seventh embodiment with reference to FIGS. 8, 11 and 12, aredisposed. The plate element 231 has its inner circumferential portionfixed to the inertia plate 211 and its outer circumferential portioninserted in the viscous fluid charged chamber and engaged with theundulated plate springs 218.

A space I is defined between a back surface of the turbine 14 and thepiston 216, a space II is defined by and between the piston 216 and theinertia plate 211, and a space III is defined by and between the inertiaplate 211 and the front cover 202. The space I and the space III areconducted to each other in their respective outer circumferentialportions. The space II is closed in the outer circumferential portionwith the friction element 116a of the piston 216 being pressed againstthe inertia plate 211. The inner circumference of space II open to thethird oil duct 148 passing through a main drive shaft 209.

In a state where the piston 116 moves to the right in FIG. 14, thefriction element 216a is detached from the inertia plate 211; that is,the lock-up clutch 210 is disengaged. Under the condition, the weight211a functions as a dynamic damper of a power input mechanism throughthe undulated plate springs 218 to dampen vibration in the engine.

In a state where the piston 216 is moved to the left in FIG. 14, thefriction element 216a is pressed against the inertia plate 211. In thissituation, as will be recognized in FIG. 15, torque is transmitted fromthe front cover 202 to the main drive shaft 209 through the undulatedplate springs 218. Under the condition, the weight 211a increases aratio of moment of inertia of a power output mechanism to a power inputmechanism. In consequence, resonance frequency is reduced to the numberof idle revolution of a speed of the vehicle or under, and occurrence ofabnormal sound like clattering sound and internal indistinct sound inthe transmission is reduced.

Embodiment 9

FIG. 16 is a schematic sectional view showing a torque converter 1i inaccordance with a ninth embodiment of the present invention.

The torque converter 1i primarily includes an impeller 13, a turbine 14and a stator 15. The impeller 13 along with a front cover 302 coupled tothe crank shaft (not shown) defines a hydraulic oil chamber. The turbine14 is coupled to the main drive shaft 309 through a turbine hub 308. Thestator 15 is placed between inner circumferential portions of theimpeller 13 and the turbine 308.

A lock-up clutch 310 is placed in a space between the front cover 302and the turbine 304. The lock-up clutch 310 primarily includes aninertia plate 311, a plurality of coil springs 312 and a piston 316.

The inertia plate 311 is a disc-shaped element disposed adjacent to thefront cover 302. An inner circumferential end of the inertia plate 311is tubular in shape, protruding toward the impeller 13, and it issupported by a thrust bearing 313 and a bush 314 so as to relativelyrotate to the front cover 302. In an outer circumference of the inertiaplate 311, an annular weight 311a is fixed. The inertia plate 311 hasits outer circumferential portion coupled to the front cover 302 througha plurality of coil springs 312.

The piston 316 is a disc-like element placed adjacent to the inertiaplate 311, and has its inner circumferential end supported by theturbine hub 308 through a bearing 319 so as to relatively rotate andmove in axial directions. In a surface of an outer circumferentialportion of the piston 316 opposed to the inertia plate 311, an annularfriction element 316a is fixed.

In the above-mentioned configuration, a clutch 350 is formed of an outercircumferential portion of the inertia plate 311 and the frictionelement 316a of the piston 316. A space I is defined by and between theback surface of the turbine 14 and the piston 316, a space II is definedby and between the piston 316 and the inertia plate 311, and a space IIIis defined by and between the inertia plate 311 and the front cover 302.The space I and the space III are open to each other in their respectiveouter circumferences. The space II is closed with the friction element316a of the piston 316 being in contact with the inertia plate 311 atits outer circumferential portion. The space II has its innercircumferential portion open to the third oil duct 148 (FIGS. 9 and 10)passing through the main drive shaft 309.

An operation of the torque converter will now be described. It should beappreciated that the hydraulic pressure control circuit 140 may be usedwith the ninth embodiment and other embodiments of the presentinvention.

In the state shown in FIG. 9, the lock-up solenoid 144 is turned off,and hydraulic oil is drained from a valve of the lock-up solenoid 144.As a result, there is no hydraulic pressure in a head of a piston of alock-up control valve 143, and the piston is pushed to the right in thedrawing by force of spring and closes a drain. In this way, the lock-upcontrol valve 143 leads the hydraulic oil from a pressure regulator 142to the third oil duct 148 (FIGS. 9 and 10). This causes hydraulicpressure to work in the space II within the torque converter 1i, so thatthe piston 316 is moved to the right in FIG. 16. Under this condition,the friction element 316a of the piston 316 is detached from the inertiaplate 311; that is, the lock-up clutch 310 is disengaged. In thissituation, the weight 311a functions as a dynamic damper of a powerinput mechanism through a coil spring 312 to dampen vibration in theengine.

When a speed of the vehicle reaches a certain level, the lock-upsolenoid 144 responds to a signal from a speed sensor not shown to turnon. Then, as shown in FIG. 10, the hydraulic pressure causes the pistonof the lock-up control valve 143 to be pushed to the left in FIG. 10,and this allows the hydraulic oil in the space II of the torqueconverter 1i is drained through the third oil duct 148 (FIGS. 9 and 10)and the lock-up control valve 343. As a result, the hydraulic pressurewithin the space II becomes lower than those in the space I and thespace III, and the piston 316 moves toward the left in FIG. 16. Underthis condition, the friction element 316a of the piston 316 is pushedagainst the inertia plate 311. In this situation, as can be seen in FIG.15, torque is transmitted from the front cover 302 to the main driveshaft 309 through the coil spring 312, and the weight 311a increases aratio of moment of inertia of a power output mechanism to a power inputmechanism. In consequence, resonance frequency is reduced to the numberof idle revolution of the speed of the vehicle engine or under, andoccurrence of abnormal sound like clattering sound and internalindistinct sound of the transmission can be reduced during an ordinarydriving.

Embodiment 10

A lock-up clutch 460 in a torque converter 1j in accordance with a tenthembodiment of the present invention is shown in FIG. 17. The lock-upclutch 460 primarily includes an inertia plate 461, a power output plate462, a piston 464 and a pair of undulated plate springs 475 disposedwithin a viscous fluid charged chamber.

The inertia plate 461 is a disc-shaped element placed on a side of thefront cover 402. The inertia plate 461 has it inner circumferential endrotatably supported by the front cover 402 by a thrust bearing 413 and abush 414. In an outer circumferential portion of the inertia plate 461,an annular weight 461a is provided.

The power output plate 462 is a disc-shaped element, and its innercircumferential end is fixed to a turbine hub 408. In opposite sidesurfaces of an outer circumferential portion of the power output plate462, an annular friction element 463 is fixed.

The piston 464 along with other plate elements defines a viscous fluidcharged chamber. The piston 464 has its inner circumferential endrotatably supported by the turbine hub 408 through a bearing 419 and itsouter circumferential end engaged with a weight 461a so as not torelatively rotate but move in axial directions. Moreover, a plateelement 476 coupled to the front cover 402 is inserted in an innercircumferential portion of the viscous fluid charged chamber and engageswith the undulated plate springs 475. In this embodiment, while thelock-up clutch 460 is disengaged, the weight 461a functions as a dynamicdamper in the front cover 402 through the undulated plate springs 475.

When the lock-up clutch 460 is engaged, torque is directly transmittedfrom the front cover 402 to the turbine hub 408 through the lock-upclutch 460. In this situation, in addition to the effects in theprevious embodiments, opposite surfaces of the power output plate 464performs torque transmission, and therefore, abrasion of the frictionelement 463 is diminished for the same capacity of the torquetransmission.

Embodiment 11

A lock-up clutch 560 of a torque converter 1k in accordance with aneleventh embodiment of the present invention is shown in FIG. 18. Thelock-up clutch 560 primarily includes an inertia plate 561, a poweroutput plate 562, a piston 564, and a coil spring 565. The inertia plate561 is a disc-shaped element placed on a side of the front cover 502.The inertia plate 561 has its inner circumferential end rotatablysupported on the front cover 502 by a thrust bearing 513 and a bush 514.In an outer circumferential portion of the inertia plate 561, an annularweight 561a is provided.

The power output plate 562 is a disc-shaped element and has its innercircumferential end fixed to a turbine hub 508. In opposite surfaces ofan outer circumferential portion of the power output plate 562, anannular friction facing 563 is fixed.

A piston 564 is a disc-shaped element placed on a side of the poweroutput plate 562. The piston 564 has its inner circumferential endrotatably supported by the turbine hub 508 through a bearing 519. Thepiston 564 has its outer circumferential end engaged with a weight 561aso as not to relatively rotate but to move in axial directions. An outercircumferential portion of the piston 564 is coupled to the front cover502 through a plurality of coil springs 506. In this embodiment, whilethe lock-up clutch 560 is disengaged, the weight 561a functions as adynamic damper in the front cover 502 through the coil springs 565.

When the lock-up clutch 560 is engaged, torque is transmitted directlyfrom the front cover 502 to the turbine hub 508 through the lock-upclutch 560. In this situation, in addition to the effects in theprevious embodiments, opposite surfaces of the power output plate 564perform the torque transmission, abrasion of the friction facing 563 isminimized for the same capacity of the torque transmission compared toprior configurations.

Embodiment 12

FIG. 19 is a schematic sectional view showing a torque converter 1l inaccordance with a twelfth embodiment of the present invention while FIG.20 is a view showing a dynamic model of the same.

A lock-up clutch 610 is placed in a space between a front cover 602 andthe turbine 14. The lock-up clutch 610 primarily includes an inertialplate 611, a pair of undulated ribbon-like plate springs 618 disposed ina viscous fluid charged chamber, a power output plate 615, and a piston616.

The inertia plate 611 is a disc-shaped element placed on a side of thesprings 618. An inner circumferential end of the inertia plate 611 istubular in shape, protruding toward a transmission, and it is supportedby a thrust bearing 613 and a bush 614 so as to relatively rotate to thefront cover 602. In an outer circumference of the inertia plate 611, anannular weight 611a is fixed.

A power output plate 615 is a disc-shaped element of which innercircumferential end fixed to a turbine hub 8, and an annular frictionelement 615a is fixed to opposite surfaces of its outer circumferentialportion.

The piston 616 is a disc-shaped element placed on a side of the poweroutput plate 615 and defines an annular viscous fluid charged chamberalong with other components. The piston 616 has its innercircumferential end rotatably supported by the turbine hub 608 through abearing 619. A plate element 631 coupled to the front cover 602 isinserted in an inner circumferential portion of the viscous fluidcharged chamber and engages with the undulated ribbon-like plate springs618.

In a configuration as mentioned above, an outer circumferential portionof the inertia plate 611, the friction element 615a of the power outputplate 615 and an outer circumferential portion of the piston 616together constitute a clutch 650.

A space I is formed by and between a back surface of the turbine 14 andthe piston 616, a space II is formed by and between the piston 616 andthe inertia plate 611, and a space III is formed by and between theinertia plate 611 and the front cover 602. The space I and the space IIIare open to each other in an outer circumferential portion. The space IIis closed in its outer circumferential portion with the piston 616pressing the friction element 615a against the inertia plate 615. Thespace II has its inner circumferential portion open to the third oilduct 148 (FIGS. 9 and 10) passing through a main drive shaft 609.

In a state where the piston 616 is moved to the right in FIG. 19, thefriction element 615a is detached from the inertia plate 611 and thepiston 616; that is, the lock-up clutch 610 is disengaged. Under thiscondition, the weight 611a is disconnected from the power inputmechanism and the power output mechanism (as defined above).

In a state where the piston 616 moves to the left in FIG. 19, thefriction element 615a is held by and between the inertia plate 611 andthe piston 616. In this situation, as can be seen in FIG. 20, torque istransmitted through the undulated ribbon-like plate springs 618.Moreover, the weight 611a increases a ratio of moment of inertia of apower output mechanism to a power input mechanism. In consequence,resonance frequency is reduced to the number of idle revolution of aspeed of the vehicle or under, and occurrence of abnormal sound likeclattering sound and internal indistinct sound in the transmission isreduced during an ordinary driving.

Embodiment 13

FIG. 21 is a schematic sectional view showing a torque converter 1m inaccordance with a thirteenth embodiment of the present invention. Thetorque converter 1m is a mechanism for transmitting torque from a crankshaft (not shown) to a main drive Shaft 709 in a transmission (notshown).

The torque converter 1m primrily includes an impeller 13, a turbine 14,and a stator 15. The impeller 13 along with a front cover 702 coupled tothe crank shaft (not shown) of an engine. The impeller 13 and the frontcover 702 constitutes a hydraulic oil chamber. The turbine 14 is coupledto the main drive shaft 709 through a turbine hub 708. The stator 15 isplaced between inner circumferential portions of the impeller 13 andturbine hub 708.

A lock-up clutch 710 is placed in a space between the front cover 702and the turbine 704. The lock-up clutch 710 primarily includes aninertia plate 711, a plurality of coil springs 712, a power output plate715, and a piston 716.

The inertia plate 711 is a disc-shaped element placed on a side of thefront cover 702. An inner circumferential end of the inertia plate 711is tubular in shape, protruding toward the impeller 13 and is supportedby a thrust bearing 713 and a bush 714 so as to relatively rotate on thefront cover 2. In an outer circumference of the inertia plate 711, anannular weight 711a is fixed.

The power output plate 15 is a disc-shaped element of which innercircumferential end is fixed to the turbine hub 8, and an annularfriction element 15a is fixed to opposite surfaces of its outercircumferential portion.

The piston 16 is a disc-shaped element placed between the power outputplate 15 and the turbine 4, and has its inner circumferential endsupported by the turbine hub 8 through a bearing 19 so as to relativelyrotate to the turbine hub 8 and to move in axial directions. Moreover,the piston 16 has its outer circumferential portion engaged with thefront cover 2 through a plurality of coil springs 12.

In a configuration as mentioned above, outer circumferential portion ofthe inertial plate 11, the friction element 15a of the power outputplate 15 and an outer circumferential portion of the piston 16 togetherconstitute a clutch 50. A space I is defined by and between a backsurface of the turbine 4 and the piston 16, a space II is defined by andbetween the piston 16 and the inertia plate 11, and a space III isdefined by and between the inertia plate 11 and the front cover 2. Thespace I and the space III are open to each other in their respectiveouter circumferential portions. The space II is closed at its outercircumferential portion with the piston 16 pressing the friction element15a against the power output plate 15. The space II has its innercircumferential portion open to the third oil duct 148 (FIGS. 9 and 10)passing through the main drive shaft 709.

An operation of the torque converter will be described below.

In a state depicted in FIG. 9, a lock-up solenoid 144 is turned off, andhydraulic oil is drained from a valve of the lock-up solenoid 144.Consequently, there is no hydraulic pressure in a head of a piston of alock-up control valve 143, and the piston is pushed to the right in thedrawing by force of a spring to close a drain. In this way, the lock-upcontrol valve 143 leads the hydraulic oil from a pressure regulator 142to the third oil duct 148. As a result, hydraulic pressure works in thespace II within the torque converter 1m, and the piston 716 moves to theright in FIG. 22. Under the condition, the friction element 715a of thepower output plate 715 is detached from the inertia plate 711 and thepiston 716; that is, the lock-up clutch 710 is disengaged. At this time,the weight 711a is released from a power input unit and a power outputunit.

When the speed of the vehicle reaches a certain level, the lock-upsolenoid 144 responds to a signal from a speed sensor (not shown) toturn on. Thus, as shown in FIG. 10, hydraulic pressure causes the piston143a of the lock-up control valve 143 to move to the left in FIG. 10, sothat the hydraulic oil within the space II of the torque converter 1m isdrained through the third oil duct 148 and the lock-up control valve143. This results in the hydraulic pressure within the space II becominglower than those in the space I and the space III, and this, in turn,causes the piston 716 to move to the left in FIG. 21. In this situation,the friction element 715a of the power output plate 715 is held by andbetween the inertia plate is 711 and the piston 716. Under thiscondition, torque is transmitted through the coil spring 712. The weight711a increases a ratio of moment of inertia of the power outputmechanism to the power input mechanism (as defined above). As a result,resonance frequency is reduced, and occurrence of abnormal sound likeclattering sound and internal indistinct sound in the transmission canbe reduced during an ordinary driving.

Embodiment 14

FIG. 22 is a schematic sectional view showing a torque converter 1n inaccordance with a fourteenth embodiment of the present invention whileFIG. 23 is a view showing a dynamic model of the same.

A lock-up clutch 810 is placed in a space between a front cover 802 anda turbine 14. The lock-up clutch 810 primarily includes an inertia plate811, a plurality of coil springs 812, a power output plate 815, a piston816, and a pair of undulated ribbon-like plate springs 818 disposedwithin the viscous fluid charged chamber.

The inertia plate 811 is a disc-shaped element placed on a side of thefront cover 802. An inner circumferential end of the inertia plate 811is tubular in shape, protruding toward the impeller 13, and it issupported by a thrust bearing 813 and a bush 814 so as to relativelyrotate to the front cover 802. In an outer circumferential portion ofthe inertia plate 811, an annular weight 811a is fixed. Moreover, theouter circumferential portion of the inertia plate 811 engages with thefront cover 802 through the coil springs 812.

The power output plate 815 is a disc-like element of which innercircumferential end is fixed to a turbine hub 808, and an annularfriction element 815a is fixed to opposite surfaces of its outercircumferential portion.

The piston 816 is a disc-like element placed between the power outputplate 815 and the turbine 14 and defines the annular viscous fluidcharged chamber along with other plate elements. The piston 816 has itsinner circumferential end supported by the turbine hub 808 through abearing 819 so as to relatively rotate to the turbine hub 808 and movein axial directions.

A plate element 831 is fixed to the front cover 802 and has its partinserted in the viscous fluid charged chamber and engaged with theundulated ribbon-like plate springs 818.

In a configuration as mentioned above, an outer circumferential portionof the inertia plate 811, the friction element 815a of the power outputplate 815 and an outer circumferential portion of the piston 816together constitute a clutch 850.

A space I is defined by and between a back surface of the turbine 14 andthe piston 816, a space II is defined by and between the piston 816 andthe inertia plate 811, and a space III is defined by and between theinertia plate 811 and the front cover 802. The space I and the space IIIare open to each other in their respective outer circumferentialportions. The space II is closed at its outer circumferential portionwith the piston 816 pressing the friction element 815a against the poweroutput plate 815. The space II has its inner circumferential portionopen to the third oil duct 148 (FIGS. 9 and 10) passing through the maindrive shaft 809.

In a state where the piston 816 moves to the right in FIG. 22, thefriction element 815a is released from the inertia plate 811 and thepiston 816; that is, the lock-up clutch 810 is disengaged. In thissituation, the weight 311a of the inertia plate 811 functions as adynamic damper against the front cover 802 because of the coil springs812 intervening therebetween to effectively dampen vibration from theengine.

In a state where the piston 816 moves to the left in FIG. 22, thefriction element 815a is held by and between the inertia plate 811 andthe piston 816. Under this condition, as can be seen in FIG. 23, torquetransmission is performed through both the coil springs 812 and theundulated ribbon-like plate springs 818. The weight 811a increases aratio of moment of inertia of a power output mechanism to a power inputmechanism with a boundary of the coil springs 812 and the undulatedribbon-like plate springs 818 therebetween. As a result, resonancefrequency is reduced to the idle speed of the vehicle, and occurrence ofabnormal sound like clattering sound and internal indistinct sound inthe transmission can be reduced during an ordinary drive.

Embodiment 15

FIG. 24 is a schematic sectional diagram showing a torque converter 1oin accordance with a fifteenth embodiment of the present invention. Thetorque converter 1o is a mechanism for transmitting torque from a crankshaft (not shown) in an engine to a main drive shaft 909 of atransmission (not shown).

The torque converter 1o primarily includes three types of runners,namely, an impeller 13, a turbine 14 and a stator 15. The impeller 13together with a front cover 902 coupled to the crank shaft (not shown)of the engine (not shown. The impeller 13 and the front cover 902 definea hydraulic oil chamber. The turbine 14 is coupled to the main driveshaft 909 through a turbine hub 908. The stator 15 is placed betweeninner circumferential portions of the impeller 13 and turbine hub 908.

A lock-up clutch 910 is placed in a space between the front cover 902and the turbine 14. The lock-up clutch 910 primarily includes an inertiaplate 911, a plurality of first coil springs 912, a power output plate915, a piston 916, and a plurality of second coil springs 917.

The inertia plate 911 is a disc-shaped element placed on a side of thefront cover 902. An inner circumferential end of the inertia plate 911is tubular in shape, protruding toward the transmission, and it issupported by a thrust bearing 913 and a bush 914 so as to rotaterelative to the front cover 902. In an outer circumferential portion ofthe inertia plate 911, an annular weight 911a is fixed. Moreover, theouter circumferential portion of the inertia plate 911 engages with thefront cover 902 through the first coil springs 912.

The power output plate 915 is a disc-like element of which innercircumferential end fixed to a turbine hub 8, and an annular frictionelement 915a is fixed to opposite surfaces of its outer circumferentialportion.

The piston 916 is a disc-like element placed between the power outputplate 915 and the turbine 14 and has its inner circumferential endsupported to the turbine hub 908 through a bearing 919 so as relativelyrotate to the turbine hub 908 and to move in axial directions. An outercircumferential portion of the piston 916 engages with the front cover902 through the second coil springs 917.

In a configuration as mentioned above, an outer circumferential portionof the inertia plate 911, the friction element 915a of the power outputplate 915 and the outer circumferential portion of the piston 916together constitute a clutch 950. A space I is defined by and between aback surface of the turbine 14 and the piston 916, a space II is definedby and between the piston 916 and the inertia plate 911, and a space IIIis defined by and between the inertia plate 911 and the front cover 902.The space I and the space III are open to each other in their respectiveouter circumferential portions to allow fluid flow. The space II isclosed at its outer circumferential portion with the piston 916 pressingthe friction element 915a against the power output plate 915. The spaceII has its inner circumferential portion conducted to the third oil duct148 (FIGS. 9 and 10) passing through the main drive shaft 909.

An operation of the torque converter will now be described.

In a state depicted in FIG. 9, a lock-up solenoid 144 is turned off, thehydraulic oil is drained from a valve of the lock-up solenoid 144. As aresult, there is no hydraulic pressure in a head of a piston 143a of alock-up control valve 143, and the piston is pushed to the right in thedrawing by force of a spring to close a drain. Thus, the lock-up controlvalve 143 leads the hydraulic pressure from a pressure regulator 142 tothe third oil duct 148. This results in the hydraulic pressure workingin the space II within the torque converter 1o, so that the piston 916is moved to the right in FIG. 24. Under this condition, the frictionelement 915a of the power output plate 915 is released from the inertiaplate 911 and the piston 916; that is, the lock-up clutch 910 isdisengaged. In this situation, the weight 911a of the inertia plate 911functions as a dynamic damper against the front cover 902 because of thefirst coil springs 912 to effectively dampen vibration from the engine.

When a speed of the vehicle reaches a certain level, the lock-upsolenoid 144 responds to a signal from a speed sensor (not shown) toturn on. Thus, as shown in FIG. 10, the hydraulic pressure causes thepiston of the lock-up control valve 143 to the left in FIG. 10, andthis, in turn, causes the hydraulic oil in the space II of the torqueconverter 1o to be drained through the third oil duct 948 and thelock-up control valve 943. As a result, the hydraulic pressure withinthe space II becomes lower than those in the space I and the space III,and consequently, the piston 916 moves to the left in FIG. 24. In thissituation, the friction element 915a of the power output plate 915 isheld between the inertia plate 911 and the piston 916. Under thecondition, which is similar to that shown in FIG. 23, torquetransmission is performed through both the first and second coil springs912 and 917 in a manner similar to springs 812 and 818 in FIGS. 22 and23. Moreover, the weight 911a increases a ratio of moment of inertia ofa power output mechanism to a power input mechanism where the boundarytherebetween is the first coil springs 912 and the second coil springs917. In consequence, resonance frequency is reduced to the number ofidle revolution of the speed of the vehicle, and occurrence of abnormalsound like clattering sound and internal indistinct sound in thetransmission can be avoided during an ordinary drive.

Various details of the invention may be changed without departing fromits spirit nor its scope. Furthermore, the foregoing description of theembodiments according to the present invention is provided for thepurpose of illustration only, and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

What is claimed:
 1. A lock-up clutch of a torque converter comprising:amain body; an impeller fixed to an inner surface of said main body; aturbine mounted within said main body adjacent to said impeller forrotation with respect to said impeller; a lock-up clutch mechanismconnected to said turbine for rotation therewith; and an undulated platespring engageable with said lock-up clutch mechanism for absorbingvibration in response to engagement of said lock-up clutch mechanism. 2.The lock-up clutch as in claim 1, wherein:said lock-up clutch comprisesa piston element selectively engageable and disengagable with a frontcover of said main body; and wherein said undulated plate spring isdisposed between said piston element and turbine, allowing limitedangular displacement therebetween.
 3. The lock-up clutch as in claim 2wherein said undulated plate spring is disposed within a viscous fluidcharged chamber formed on said piston element.
 4. The lock-up clutch asin claim 2 wherein said undulated plate spring is disposed within aviscous fluid charged chamber formed on a front cover of said main body.5. The lock-up clutch as in claim 1, wherein said undulated plate springis formed with a plurality of arcuate portions and a plurality of leverportions which alternate and are unitarily formed, and alternating pairsof said lever portions are provided with a hole for viscous fluidpassage.
 6. The lock-up clutch as in claim 1, further comprising;aweight element disposed between a front cover of said main body and saidturbine; a piston element coupled to said turbine, said piston elementconfigured for coupling and uncoupling from said weight element; ahydraulic pressure control device controlling hydraulic pressure withinsaid main body for controlling coupling and uncoupling of said pistonelement from said weight element; and said undulated plate springelastically coupling said weight element with the front cover incircular directions.
 7. A lock-up clutch comprising:a main body; animpeller fixed to an inner surface of said main body; a turbine mountedwithin said main body adjacent to said impeller for rotation withrespect to said impeller; a lock-up clutch mechanism connected to saidturbine; a spring coupled to said lock-up clutch mechanism for absorbingvibration in response to engagement of said lock-up clutch mechanism; aweight element disposed between a front cover of said main body and saidturbine; a piston element coupled to said turbine, said piston elementconfigured for coupling and uncoupling from said weight element; ahydraulic pressure control device controlling hydraulic pressure withinsaid main body for controlling coupling and uncoupling of said pistonelement from said weight element; and said spring elastically couplingsaid weight element with the front cover in circular directions.
 8. Thelock-up clutch as in claim 7 wherein said spring is a coil spring. 9.The lock-up clutch as in claim 7 wherein said spring is an elongatedundulated plate spring.